When an electric window lifter motor of a window lifter fully closes a window pane, the window lifter motor is rotationally driven to close the window pane until the window pane presses against an associated seal on the window frame with a desirably high amount of force, causing the window pane to come to a stop. The window lifter motor is blocked when the window pane is stopped by the seal, causing a high blocking current (e.g., 30A) to flow through the window lifter motor. This is acceptable as long as the blocking current flows through only one window lifter motor in the vehicle.
However, currently available comfort functions in vehicles are able to close all of the window panes of the vehicle simultaneously. In fact, some consumers find it disturbing when, in spite of identical starting positions, different window panes in the vehicle reach the fully closed position at different times even though the associated window lifters received the instruction to close the window panes at the same time. But if all of the window panes are actually closed at the same time, this can result in as many as four window lifter motors being supplied with the blocking current at the same time. The high amount of blocking current to the window lifter motors leads to a noticeable voltage drop in the power supply of the vehicle. This voltage drop is especially critical if the vehicle is provided with other electric systems which have high power requirements themselves, such as an electrical steering system (“steer-by-wire”) or an electrical brake system (“brake-by-wire”). As soon as a control unit in such systems detects the voltage drop, the system may be momentarily disconnected until the voltage drop is over. Obviously, however, it is undesirable in an electrical steering system or an electrical brake system for a functional interruption to occur.
There is a desire for a window lifter system in which, on the one hand, can meet the demands in relation to comfort (e.g., simultaneous window closing) made by the ultimate customers and, on the other hand, avoids voltage drops in the on-board supply when meeting those demands.